(a) A 3.00-L flask is filled with gaseous ammonia, NH3. The gas pressure measure

Question

(a) A 3.00-L flask is filled with gaseous ammonia, NH3. The gas pressure measured at 18.0 C is 1.65 atm . Assuming ideal gas behavior, how many grams of ammonia are in the flask?

Express your answer to three significant figures and include the appropriate units.

(b) If 1.00 mol of argon is placed in a 0.500-L container at 30.0 C , what is the difference between the ideal pressure (as predicted by the ideal gas law) and the real pressure (as predicted by the van der Waals equation)?

For argon, a=1.345(L2atm)/mol2 and b=0.03219L/mo

Explanation / Answer

1) Moles of ammonia present , n = (P*V)/(R*T) = (1.65*3)/(0.0821*291) = 0.207

Molar mass of ammonia = 17 g/mole

Thus, mass of ammonia = moles*molar mass = 0.207*17 = 3.522 g

2) As per Ideal Gas Equation,pressure = (n*R*T)/V = 1*0.0821*303/0.5 = 49.753 atm

As per Vander Waal's equation,

(P + n2a/V2)*(V - nb) = n*R*T

or, (P + (1*1.345/0.25))*(0.5 - 1*0.03219) = 1*0.0821*303

or, P = 47.796 atm

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